Preparation and characterization of the catalyst system Fe sub 2 O sub 3 /ZrO sub 2 and preparation and characterization of the high T sub c superconducting copper oxide compounds

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6837728

Davison, S C

Tetragonal ZrO{sub 2} was prepared by decomposing either the basic carbonate or basic nitrate and by precipitation from a zirconium salt solution using base. The oxide products obtained were characterized by their surface areas and crystallite size, and the methods of preparation compared. All methods produced high surface area materials suitable for catalytic supports. Transformation of the tetragonal to the monoclinic phase was studied. Samples of Cubic ZrO{sub 2} containing 2.5 at % - 40 at % Fe(III) were prepared by codecomposition of the nitrates. Characterization showed that {alpha}-Fe{sub 2}O{sub 3} and ZrO{sub 2} form a solid solution up to 25 at % Fe/Zr in the product. At this point, the solubility limit of {alpha}-Fe{sub 2}O{sub 3} in ZrO{sub 2} is exceeded. The reduction of cubic zirconia samples containing 2.5 at%-20 at% Fe(III) leads to the stabilization of iron(II) in the zirconia lattice. Reduction to metallic iron occurs at much higher temperatures than the reduction of bulk {alpha}-Fe{sub 2}O{sub 3}. The bulk magnetic properties of iron oxide were also studied as a functional of crystallite size. The superconducting oxides La{sub 1.8}Sr{sub .2}CuO{sub 4} and Ba{sub 2}YCu{sub 3}O{sub 7} were prepared by decomposition of mixed metal nitrates. Measurements on La{sub 1.8}Sr{sub .2}CuO{sub 4} indicated the removal of the localized Cu(II) found in the parent compound La{sub 2}CuO{sub 4} as a result of delocalization. The compound Ba{sub 2}YCu{sub 3}O{sub 7} prepared from the nitrates and subjected to a low temperature oxygen anneal gave a sharp superconducting transition at 92 K. The phase was stoichiometric but readily decomposed when kept in contact with moist air.

• Research Organization: Brown Univ., Providence, RI (USA)
• OSTI ID: 6837728
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CATALYST SUPPORTS
CHALCOGENIDES
CHEMICAL PREPARATION
COPPER COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
IRON COMPOUNDS
IRON OXIDES
LANTHANUM COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
STRONTIUM COMPOUNDS
SUPERCONDUCTIVITY
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES